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Magnetoelastic excitations in the pyrochlore spin liquid Tb2Ti2O7
T Fennell1, M Kenzelmann2, B Roessli1
1Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
Physical Review Letters
|February 4, 2014
Summary
Terbium titanate (Tb2Ti2O7) exhibits a unique spin liquid state. This state features a hybrid excitation coupling crystal fields and acoustic phonons, suppressing magnetic order.
Area of Science:
- Condensed matter physics
- Materials science
- Quantum magnetism
Background:
- The material Tb2Ti2O7 was expected to exhibit magnetic order or structural distortion at low temperatures.
- Instead, it enters a spin liquid state, defying initial predictions.
Purpose of the Study:
- To investigate the nature of the spin liquid state in Tb2Ti2O7.
- To understand the mechanism suppressing magnetic order and structural distortion.
Main Methods:
- Neutron scattering experiments were employed to probe the low-temperature state of Tb2Ti2O7.
- Analysis focused on identifying and characterizing excitations within the spin liquid phase.
Main Results:
- A novel hybrid excitation was discovered, coupling an excited crystal field level to a transverse acoustic phonon.
- Identical dispersion relations were observed for magnetic and phononlike branches, indicating strong hybridization.
- This hybridization was found to vanish in the paramagnetic state.
Conclusions:
- Tb2Ti2O7 is characterized as a "magnetoelastic spin liquid" due to the observed excitation hybridization.
- The magnetoelastic coupling is proposed to be the mechanism that suppresses both magnetic ordering and structural distortion.
- The spin liquid phase is described as a Coulomb phase with propagating bosonic spin excitations.
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